You often want different angles if you are using outriggers. The rod to the outrigger is more upward than the line that goes straight off the back of the boat. This helps with line management and prevents tangles.
If you are using a rod holder for use with an outrigger tube, you need a 45. Normal is a 30, and 15 is used for the rod to the outrigger. Also consider not running all of them straight back - angle some out a bit, particularly the 15 to the outrigger.
So from the back up, you would have a 30 in the rear, a 15 (or 30 if you prefer and don't use outriggers) at mid-point angled outboard a bit (whatever the gunnel will handle), and a 45 above that (almost in line with the console). I put an extra 30 in between the front and the 2nd because it's easy to get to when trolling. My front one is actually an 45 outrigger base, but can be used as a rod holder.
Check out the diagram below to get the idea:
